Often a plurality of wells penetrating and in fluid communication with a subterranean hydrocarbon-bearing formation are utilized to inject fluids into and/or produce fluids, including hydrocarbons, from a portion of the formation or the entire formation. In this manner, areal conformance of the fluids injected into or produced from the formation can be improved thereby increasing hydrocarbon recovery. Where a portion of the subterranean formation is being produced, these wells can be arranged in conventional linear, 5-spot, 7-spot, etc., patterns, or arrays, or where an entire formation is to be produced, the plurality of wells can be arranged in, for example, concentric ring patterns or arrays. Ideally, if fluid could be injected into all designated injection wells of such a multiwell system at rates which would result in uniform or balanced flood fronts and/or if fluids could be produced from all designated production wells of a multiwell system at rates which would maintain a uniform or balanced flood front, the areal conformance of fluids injected into and/or produced from a subterranean formation would be maximized. In actuality, one or more injection wells are characterized by a significantly greater fluid injection rate than other designated injection wells of multiwell system, and/or one or more production wells are characterized by a significantly greater fluid production rate than other designated production wells of a multiwell system resulting in relatively poor areal conformance of fluids injected into and/or produced from the formation.
Prior art attempts to reduce the fluid injection rate or production rate of certain wells of a multiwell system in order to improve areal conformance of fluids injected into or produced from a subterranean formation have been relatively unsuccessful. One prior art approach involves the injection of well cement into an injection or production well to reduce the injection rate into or production rate from the well. However, as placement of the cement is extremely difficult to control, such approach often results in either plugging only a portion of the entire well bore interval over which fluid can be injected into or produced from the formation, or in entirely terminating or shutting off flow of fluids into or from the well bore. Other prior art attempts have employed aqueous fluids having reactive species dissolved therein which are sequentially injected into a well bore interposed by an aqueous spacer medium. These fluids eventually penetrate the aqueous spacer and mix at a substantial distance from the well bore. The species dissolved in the sequentially injected aqueous fluids react upon mixing to form a plugging precipitate. However, as radial flow of fluids injected into or produced from a well is predominantly influenced by the near well bore environment, failure of this prior art approach to reduce the permeability of the near well bore environment over the entire well bore interval has resulted in relatively poor areal conformance improvement of fluids injected into or hydrocarbons produced from a subterranean formation via a multiwell system.
Thus, a need exists for a process which selectively and predictably reduces the fluid injection rate or production rate of one or more wells of a multiwell system by effectively reducing the permeability in the near well bore environment so as to improve areal conformance of fluids injected into and/or produced from a subterranean formation via the multiwell system.